Abstract:

Studies were conducted on the distribution, fate and metabolism of DDT in a model ecosystem simulating a tropical marine environment of fish, Gabions nudiceps, Leihrinuf haruk, Cohious keineiis, Gnhiota nebutosis and white shrimp iPanaeus seliferus), show that DDT concentration in the water decreases rapidly within the first 24 h. Rapid accurr. • ution of the pesticide in the biota also reaches a maximum level in 24 h before graJuiiiy declining The bioaccumulution factors calculated for the fish specie.! (G. keinesis) and white shrimp '(P. Stiiferu!) were 270 and 351, respectively, after 24 h There was a steady build up of DDT residues in the sediment during the first 24 h which continued to a maximum concentration of 6 66 ng g in the sea-water fish sediment ecosystem after 3 weeks and 5.27ngg in the seawater/shrimps/sediment ecosystem after 2.7 days The depuration of the accumulated pesticide was slow with only 54% lost in G. nudiceps within 3 days of exposure in fresh sea water. By contrast, depuration was fast in the while shrimp, which lost 97% of the accumulated pesticide under the same conditions. DDT was found to be toxic to two of the fish species, (G. nebulmis and /_. huruk) and to white shnmp, and the degree of toxicity was dependent on the particular species. The 24 h LCyj al room temperature lor the fish species G. nebulous and white shrimp was found to be 0.011 and O.I 16mg kg. respectively. These levels are comparable to the ones recorded for the temperate organisms. Degradation of DDT to its primary metabolites. DDE and DDD. uas found in all the compartments of the ecosystem with DDE being the major metabolite in the fish, shrimps and sediment, while in se.iwater. DDD dominated as the major metabolite.